The present invention is related to a method for deformation of a material body, in which a stamping member with a mass m is conveyed towards and hits a material body with such a velocity that at least one rebound motion of the stamping member is generated, while a permanent deformation of the body is generated. The invention also relates to a device for deformation of a material body, comprising a stamping member arranged to be conveyed towards and hit a material body with such a velocity that a rebound motion of the stamping member is generated, while a permanent deformation of the material body is generated.
Through the earlier patent application No. WO 97/00751 of the applicant it is known to fix a material body, either in solid form or in form of a powder of grain, pellets or similar and with one single or several consecutive strokes by means of a striking unit achieve adiabatic coalescence in the material body, through which a fast and effective deformation of the material body is obtained.
According to this prior art, when a plurality of consecutive strokes is applied to the body, the interval between the consecutive strokes should be smaller than approximately 0,2 seconds. At compacting of powder, preferably metal powder, it is suggested that three consecutive strokes are applied to the material body. Of these strokes, the first one is an extremely light stroke forcing the most of the air out of the powder and orientating the powder particles. The next stroke has very high energy and high striking velocity in order to achieve local adiabatic coalescence of the powder particles so that these are pressed together to extremely high density. The third stroke has medium high energy, i.e. lower energy than the second stroke, and achieves final shaping of the material body, which subsequently can be sintered. At corresponding deformation of a solid metal body, sliding planes will be activated during a large local temperature increase in the material, through which the required deformation is achieved.
In both the described cases, however, a very powerful impulse from the striking unit will be required to achieve the intended deformation effect when one single stroke or several strokes at intervals of in the order 200 ms are used to achieve the desired goal. The striking tool, or the stamping member, is allowed to bounce back between every single stroke. It is thereby not in contact with the material body between the strokes, only once per stroke. The stroke or the strokes give a locally very powerful increase of the temperature in the material of the deformed body. When the material of the body comprises one or several metals or metal alloys, such a powerful temperature increase usually results in phase transitions of the material, both when heating it and subsequently cooling it. The cooling can further often be done relatively fast, since the temperature increase often is local and the heat can be carried off via the surrounding, colder material. The probability is high that unwanted structures and phases, for instance martensite in steel, are obtained as a result of this process.